Method of locking 1α-OH of vitamin D compounds in axial orientation

ABSTRACT

A method of modifying or altering the structure of a 1α-hydroxylated vitamin D compound to increase its biological activity by altering the conformational equilibrium of the A-ring to favor a chair conformation that presents the 1α-hydroxyl in the axial orientation. This is accomplished by either locking the A-ring chair conformation in a geometry having an axially orientated 1α-hydroxyl, or by the addition of one or more substituents to the A-ring which interact with other substituents in the molecule or on the A-ring to provide a driving force to the A-ring to adopt a chair conformation which presents the 1α-hydroxyl in the axial orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/241,555 filed Sep. 11, 2002 now U.S. Pat. No. 6,890,914 which inturn is a divisional of U.S. patent application Ser. No. 10/001,623filed Oct. 31, 2001, now U.S. Pat. No. 6,506,912, which in turn is adivisional of U.S. patent application Ser. No. 09/553,206 filed Apr. 20,2000, now U.S. Pat. No. 6,369,099, which in turn is a divisional of U.S.patent application Ser. No. 09/082,776 filed May 21, 1998, now U.S. Pat.No. 6,114,317.

STATEMENT REGARDING FEDERALLY SPONSERED RESEARCH OR DEVELOPMENT

This invention was made with United States government support awarded bythe following agencies:

-   -   NIH Grant No. DK14881        The United States has certain rights in this invention.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to vitamin D compounds, and moreparticularly, to a method of presenting the 1α-OH of vitamin D compoundsin an axial orientation and the compounds made thereby.

The two diastereomeric forms of monosubstituted cyclohexanes (Scheme I)are differently populated, the equilibrium constant K being given by theequationΔG°=−RT1n Kwhere K=[equatorial conformer]/[axial conformer]. ΔG° (usually negative)is the difference of free energy between the equatorial and axialconformers and −ΔG° is known as conformational free energy of thesubstituent R [defined as it's A value, Winstein et al., J. Am. Chem.Soc. 77, 5562 (1955)]. Thus, the greater the A value of the substituentR, the greater a driving force to adopt the R-equatorial form. A valuecan be, therefore, considered as

destabilization energy imparted to a monosubstituted six-membered chairby an axial substituent. Thus, for example, the A value of methylsubstituent equals ca. 1.7 kcal/mol [Hirsch, Top. Stereochem. 1, 199(1967)] that corresponds to 95% of population of equatorial conformer ofmethylcyclohexane at room temperature. The conformational free energiesof substituents in cyclohexanes under ideal conditions are expected tobe additive. It is usually assumed that all conformational effects areadditive, i.e. various destabilizing interactions identified within asix-membered ring system operate independently of each other. In di-,tri- and polysubstituted cyclohexanes mutual interactions among thesubstituents have to be considered. Such interactions can destabilizeone chair conformation raising its energy to favor an alternate invertedchair form, or even favor some other, distorted (rigid or flexible)cyclohexane geometries. The most important interactions that influencethe equilibrium between the respective chair conformations includeinteraction of a pair of substituents in 1,2-trans-diequatorial and1,3-cis-diaxial relationship. Thus, total destabilization energy (E_(D))can be described as a sum of the substituents' A values, representingmonoaxial interactions, G values for 1,2-diequatorial interactions and Uvalues for 1,3-diaxial interactions [Corey, et al., 3. Org. Chem. 45,765 (1980)].E _(D)=Σ(A+G+U)

In the case of alkylidenecyclohexanes, additional interactions areinvolved, especially in 2-substituted derivatives. The most importantinteraction (designated A^(1,3)-strain, Johnson, Chem. Rev. 68, 375(1968)] exists in the allylic segment between equatorial R₁ andsubstituent R₂ of the exomethylene unit (Scheme II). When both

R₁ and R₂ are medium or large groups, the axial conformer is preferredover the equatorial (Malhotra et al., J. Am. Chem. Soc. 87, 5492(1965)]. Thus, for example, when R₁═R₂=Me the difference in energybetween both forms is approximately 4.5 kcal/mol, in favor of the axialconformer. In the case when R₁=Me and R₂=H, a 1:3 peri interactionexists which increases by ca. 1.25 kcal/mol the destabilization energyof the system (Duraisamy et al., J. Am. Chem. Soc. 105, 3264 (1983)].

Conformational behavior of vitamin D has attracted considerableattention over the past 25 years. It has been suggested long ago[Havinga, Experientia 29, 1181 (1973)] that vitamin D compounds canexist as a mixture of two rapidly equilibrating A-ring chair conformers.These two conformations were abbreviated as α- and β-forms (Scheme III).¹H NMR studies of vitamin D₂ and D₃ in chloroform solutions confirmedthe existence of the dynamic equilibrium between the two chair forms [LaMar et al., J. Am. Chem. Soc. 96, 7317 (1974); Wing et al., J. Am. Chem.Soc. 97, 4980 (1975)] of these B-ring secosteroids. A similarconformational equilibrium has also been found for 25-hydroxyvitamin D₃(25-OH-D₃), 1α-hydroxyvitamin D₃ (1α—OH-D₃) and the natural hormone1α,25-dihydroxyvitamin D₃ (1α,25-(OH)₂D₃) as well as some other A-ringsubstituted vitamin D derivatives [see for example Helmer et al., Arch.Biochem. Biophys. 241, 608 (1985); Sheves et al., J. Org. Chem. 42, 3597(1977); Berman et al., J. Org. Chem. 42, 3325 (1977); Sheves et al., J.Chem. Soc. Chem. Commun. 643 (1975); Okamura et al., J. Org. Chem. 43,574 (1978)]. In the α-chair conformer of vitamin D molecule, the hydroxygroup is equatorial whereas in the β-chair conformer the hydroxy groupis axially oriented.

NMR studies of various vitamin D compounds in solutions have also shownthat the ratio of the respective A-ring conformers depends significantlyon the solvent used [Helmer et al., Arch. Biochem. Biophys. 241, 608(1985)]. Unfortunately, due to solubility problems, it is impossible tostudy these conformer populations in an aqueous medium. X-Raydiffraction studies of vitamin D₂ and D₃ confirmed that their A-ringsalso occur in the solid phase as an equimolar mixture of such extreme α-and β-chair conformations [Hull et al., Acta Cryst., Sect. B, 32, 2374(1976); Trinh et al., J. Org. Chem. 41, 3476 (1976)]. Interestingly,25-OH-D₃ exists in the solid state exclusively in the α-form whereas thenatural hormone 1α,25-(OH)₂D₃ in the A-ring β-form [Trinh et al., J.Chem. Soc., Perkin Trans. II, 393 (1977); Suwinska et al., Acta Cryst.,Sect. B, 52, 550 (1996)]. X-Ray studies have also shown that theC(5)=C(6)–C(7)=C(8) diene part of the molecule is nearly planar, whereasthe exocyclic C(10)=C(19) bond, because of steric strain, is twisted outof plane by about 55°. This exomethylene group is situated below themean A-ring plane in the α-chair form and above it in the alternateβ-chair form. In the case of vitamin D analogs substituted in the ring Awith a 1α-hydroxy group, crucial for biological activity, theorientation of 1α-OH is axial in the α chair form and equatorial in theβ-form (Scheme IV).

It has to be added that molecular mechanics calculations revealed that,similarly as in the case of the model 1,2-dimethylenecyclohexane([Hofmann et al., J. Org. Chem. 55, 2151 (1990)], an existence of otherthan low-energy chair conformations of the ring A can be expected for Dvitamins, namely, half-chair or twist forms [Mosquera et al., J. Mol.Struct. 168, 125, (1988); Hofer et al., Monatsh. fur Chemie, 124, 185(1993)].

In 1974, it was proposed [Okamura et al., Proc. Natl. Acad. Sci. USA 71,4194 (1974); Wing et al., Science 186, 939 (1974)] that calciumregulation ability of vitamin D is limited to the compounds that canassume a ring-A chair conformation in which the 1α-hydroxy group (orpseudo-1α-OH) occupies an equatorial orientation. Such conformation,according to this hypothesis, has the proper geometry for binding to theprotein receptor, a step which is necessary to induce the biologicalresponse leading to the calcium transport and calcium mobilization inthe body. However, recent results of biological testing of1α,25-dihydroxy-10, 19-dihydroxyvitamin D₃ compounds do not support theidea that the equatorially favored 1-hydroxyl would be the mostbiologically active. On the contrary, 1α,25-dihydroxy-10(S),19-dihydrovitamin D₃, the analog strongly biased toward the A-ring chairconformer possessing 1α-axial orientation, provided the greatest in vivobiological response and showed very significant activity on intestinalcalcium transport. Moreover, more recent studies on 19-norvitamins,especially those substituted at C-2, demonstrate that pronouncedbiological activity is provided by compounds having an axial1α-hydroxyl. Thus, it is believed that axial orientation of the1α-hydroxyl group in the vitamin D molecule is of crucial importance forits biological activity and, the prediction of its biological responsecan be made by evaluation of the conformational equilibrium of theA-ring of the vitamin. It is believed that the more favored the axialposition of 1α-hydroxyl is the greater biological response can beexpected. A logical extension of this prediction is that the greatestactivity can be predicted for such A-ring substitution of vitamin Dmolecules which:

1) constitute anancomeric system or other corresponding to at least 90%preponderating conformer possessing 1α-OH in axial position, even thoughthe rate of A-ring inversion can remain facile—these analogs arecharacterized by conformationally free well-defined geometries of Arings and a significant energy advantage (at least 1.2 kcal/mole) for anaxial 1α-OH conformer; or 2) constitute conformationally locked, rigidor distorted geometries in which the A ring is held in only one chairconformation, i.e. the one having an axial 1α-OH or, although it maydeform considerably, it may not flip over to its conformationallyinverted opposite form with equatorial orientation of 1α-OH.

Such structural constrains which prevent the cyclohexane ring fromflipping but which can be accommodated by its chair geometry (Scheme V)include:

1) anchoring bonds (trans-fusion bonds to a ring of size seven orsmaller),

2) flattening bonds (fusion bonds to a ring of size seven or smallerwhich contains a double bond exocyclic to the six-membered ring), and

3) bridged bonds (two contiguous ring bonds whose termini are joined bya bridge of five atoms or fewer).

It should be noted that the remaining substituents (or hydrogens) offlattening or anchoring bonds must assume an axial orientation withrespect to the six-membered ring. In the case of (1,3)-bridging, thebridged bonds have to be axially disposed with respect to thesix-membered ring.

Accordingly, the present invention provides a novel class of1α-hydroxylated vitamin D compounds wherein the conformationalequilibrium of the A-ring has, or has been altered or modified to favora chair conformation that presents the 1α-hydroxyl in the axialorientation, and the A-ring is attached to the conventional 5,7-dieneand C-D ring system having any known side chain attached at carbon 17 ofthe D-ring.

Structurally these novel analogs are characterized by the generalformula I shown below:

where Y₁ and Y₂, which may be the same or different, are each selectedfrom the group consisting of hydrogen and a hydroxy-protecting group;where Y₃, Y₄, Y₅, Y₆, Y₇ and Y₈, which may be the same or different, areeach selected from the group consisting of hydrogen, a methyl group orsubstituted methyl group of the formula —CR₁R₂R₃, an amino group orsubstituted amino group of the formula —NR₁R₂, a phosphino group orsubstituted phosphino group of the formula —PR₁R₂, an alkylsulfinylgroup, an arylsulfinyl group, an alkylsulfonyl group, an arylsulfonylgroup, and aryl, where R₁, R₂ and R₃ are each independently selectedfrom the group consisting of hydrogen, C₁₋₅ alkyl, hydroxyalkyl,aminoalkyl, halogenalkyl, alkoxyalkyl, aryloxyalkyl, aryl, halogen,hydroxyl, protected hydroxy, alkoxyl, aryloxyl, acyl, an amino group, analkyl substituted amino group, and an aryl substituted amino group, andwhere R₁ and R₂ taken together represent an oxo group or a group—CH₂)_(m)— where m is an integer having a value of from 2 to 5; or Y₃and Y₄ when taken together represent a methylene group; or Y₇ and Y₈when taken together represent a methylene group; where Y₂ and Y₆, or Y₂and Y₇, when taken together may represent the group —(CR₁R₂)_(n)— wheren is an integer having a value of from 1 to 4 and wherein any of thegroups —CR₁R₂— may be replaced by an oxygen, sulfur or nitrogen atom;where Y₅ and Y₈, or Y₅ and Y₃, or Y₃ and Y₈, when taken together mayrepresent the group —CR₁R₂)_(r)— where r is an integer having a value offrom 1 to 5 and wherein any of the groups —CR₁R₂— may be replaced by anoxygen, sulfur or nitrogen atom; and where Y₅ and Y₆ when taken togetherrepresent the group ═CR₄R₅ where R₄ and R₅, which may be the same ordifferent, are each selected from the group consisting of hydrogen andY₃, with the proviso that R₄ and R₅ cannot be a hydroxyl; and where R₄and Y₂ when taken together may represent the group —CR₁R₂)_(s)— where sis an integer having a value of from 1 to 3; and where the group Rrepresents any of the typical side chains known for vitamin D typecompounds.

More specifically R can represent a saturated or unsaturated hydrocarbonradical of 1–35 carbons, that may be straight-chain, branched or cyclicand that may contain one or more additional substituents, such ashydroxy- or protected-hydroxy groups, fluoro, carbonyl, ester, epoxy,amino or other heteroatomic groups. Preferred side chains of this typeare represented by the structure below

where the stereochemical center (corresponding to C-20 in steroidnumbering) may have the R or S configuration, (i.e. either the naturalconfiguration about carbon 20 or the 20-epi configuration), and where Zis selected from Y, —OY, —CH₂OY, —C≡CY and —CH═CHY, where the doublebond may have the cis or trans geometry, and where Y is selected fromhydrogen, methyl, —COR₁₀ and a radical of the structure:

where x and y, independently, represent the integers from 0 to 5, whereR₆ is selected from hydrogen, deuterium, hydroxy, protected hydroxy,fluoro, trifluoromethyl, and C₁₋₅-alkyl, which may be straight chain orbranched and, optionally, bear a hydroxy or protected-hydroxysubstituent, and where each of R₇, R₈, and R₉, independently, isselected from deuterium, deuteroalkyl, hydrogen, fluoro, trifluoromethyland C₁₋₅ alkyl, which may be straight-chain or branched, and optionally,bear a hydroxy or protected-hydroxy substituent, and where R₆ and R₇,taken together, represent an oxo group, or an alkylidene group, ═CR₇R₈,or the group —CH₂)_(p)—, where p is an integer from 2 to 5, and where R₈and R₉, taken together, represent an oxo group, or the group —CH₂)_(q)—,where q is an integer from 2 to 5, and where R₁₀ represents hydrogen,hydroxy, protected hydroxy, or C₁₋₅ alkyl and wherein any of theCH-groups at positions 20, 22, or 23 in the side chain may be replacedby a nitrogen atom, or where any of the groups —CH(CH₃)—, —CH(R³)—, or—CH(R²)— at positions 20, 22, and 23, respectively, may be replaced byan oxygen or sulfur atom.

The wavy line to the substituent at C-20 indicates that the carbon 20may have either the R or S configuration.

Specific important examples of side chains with natural20R-configuration are the structures represented by formulas (a), (b),(c), (d) and (e) below, i.e. the side chain as is occurs in25-hydroxyvitamin D₃ (a); vitamin D₃ (b); 25-hydroxyvitamin D₂ (c);vitamin D₂ (d); and the C-24 epirner of 25-hydroxyvitamin D₂ (e):

The above novel compounds wherein the 1α-OH group is presented in theaxial orientation exhibit a desired, and highly advantageous, pattern ofbiological activity. These compounds are characterized by having greaterbiological activity, as compared to 1α,25(OH)₂D₃, in one or more of thethree activities typically referred to as “calcemic” activities, i.e.intestinal calcium transport activity, bone mineralization activity andbone calcium mobilization activity, or in cell differentiation activity.Hence, these compounds may be highly specific in their calcemicactivity. Their preferential calcemic activity suggests the in vivoadministration of these compounds for the treatment of metabolic bonediseases where bone loss is a major concern. Because of theirpreferential calcemic activity on bone, one or more of these compoundsmay be preferred therapeutic agents for the treatment of diseases wherebone formation is desired, such as osteoporosis, especially low boneturnover osteoporosis, steroid induced osteoporosis, senile osteoporosisor postmenopausal osteoporosis, as well as hypoparathroidism,osteomalacia and renal osteodystrophy. In addition, hypocalcemia as wellas rickets, and vitamin D resistant rickets may be treated with one ormore of the disclosed compounds. These compounds may also provide amethod of treating female infertility in female mammals. The treatmentmay be transdermal, oral (in solid or liquid form) or parenteral. Thecompounds may be present in a composition in an amount from about 0.01μg/day to about 100 μg/day, preferably about 0.1 μg/gm to about 50 μg/gmof the composition, and may be administered in dosages of from about 0.1μg/day to about 50 μg/day.

The compounds of the invention are also especially suited for treatmentand prophylaxis of human disorders which are characterized by animbalance in the immune system, e.g. in autoimmune diseases, includingmultiple sclerosis, diabetes mellitus, host versus graft reaction, andrejection of transplants; and additionally for the treatment ofinflammatory diseases, such as rheumatoid arthritis and asthma, as wellas the improvement of bone fracture healing and improved bone grafts.Acne, alopecia, skin conditions such as dry skin (lack of dermalhydration), undue skin slackness (insufficient skin firmness),insufficient sebum secretion and wrinkles, and hypertension are otherconditions which may be treated with one or more of the compounds of theinvention.

The above compounds may also be characterized by high celldifferentiation activity. Thus, these compounds may also providetherapeutic agents for the treatment of psoriasis and other skindisorders characterized by proliferation of undifferentiated skin cells,e.g. dermatitis, eczema, solar keratosis and the like, or as ananti-cancer agent, especially against leukemia, colon cancer, breastcancer and prostate cancer. The compounds may be present in acomposition to treat disorders such as psoriasis in an amount from about0.01 μg/gm to about 100 μg/gm of the composition, and may beadministered topically, transdermally, orally (in solid or liquid form)or parenterally in dosages of from about 0.01 μg/day to about 100μg/day.

This invention also provides a novel method of modifying or altering thestructure of a 1α-hydroxylated vitamin D compound to increase itsbiological activity by altering the conformational equilibrium of theA-ring of the 1α-hydroxylated vitamin D compound to favor a chairconformation that presents the 1α-hydroxyl in the axial orientation.This is accomplished by either locking the chair conformation of theA-ring in a geometry having an axially orientated 1α-hydroxyl, or by theaddition of one or more substituents to the A-ring which interact withother substituents in the molecule or on the A-ring to provide a drivingforce to the A-ring to adopt a chair conformation which presents the 1a-hydroxyl in the axial orientation.

DETAILED DESCRIPTION OF THE INVENTION

As used in the description and in the claims, the term“hydroxy-protecting group” signifies any group commonly used for thetemporary protection of hydroxy functions, such as for example,alkoxycarbonyl, acyl, alkylsilyl or alkylarylsilyl groups (hereinafterreferred to simply as “silyl” groups), and alkoxyalkyl groups.Alkoxycarbonyl protecting groups are alkyl-O—CO— groupings such asmethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl,butoxycarbonyl, isobutoxycarbonyl, tert-butoxycarbonyl,benzyloxycarbonyl or allyloxycarbonyl. The term “acyl” signifies analkanoyl group of 1 to 6 carbons, in all of its isomeric forms, or acarboxyalkanoyl group of 1 to 6 carbons, such as an oxalyl, malonyl,succinyl, glutaryl group, or an aromatic acyl group such as benzoyl, ora halo, nitro or alkyl substituted benzoyl group. The word “alkyl” asused in the description of the claims, denotes a straight-chain orbranched alkyl radical of 1 to 10 carbons, in all its isomeric forms.Alkoxyalkyl protecting groups are groupings such as methoxymethyl,ethoxymethyl, methoxyethoxymethyl, or tetrahydrofuranyl andtetrahydropyranyl. Preferred silyl-protecting groups are trimethylsilyl,triethylsilyl, t-butyldimethylsilyl, dibutylmethylsilyl,diphenylmethylsilyl, phenyldimethylsilyl, diphenyl-t-butylsilyl andanalogous alkylated silyl radicals. The term “aryl” specifies a phenyl-,or an alkyl-, nitro- or halo-substituted phenyl group.

A “protected hydroxy” group is a hydroxy group derivatised or protectedby any of the above groups commonly used for the temporary or permanentprotection of hydroxy functions, e.g. the silyl, alkoxyalkyl, acyl oralkoxycarbonyl groups, as previously defined. The terms “hydroxyalkyl”,“deuteroalkyl”, “aminoalkyl”, “halogenalkyl”, “alkoxyalkyl”,“aryloxyalkyl”, and “fluoroalkyl” refer to an alkyl radical substitutedby one or more hydroxy, deuterium, amino, halogen, alkoxy, aryloxy, orfluoro group respectively. A “halogen” group includes any of the fiveelements fluorine, chlorine, bromine, iodine and astatine that form apart of group VIIA of the periodic table.

As previously discussed, the novel analogs of the present invention arecharacterized by the general formula I shown below:

where the definitions of Y₁, Y₂, Y₃, Y₄, Y₅, Y₆, Y₇, Y₈ and R are aspreviously set forth herein. The preferred analogs are the following:1. 2-substituted 1α-hydroxy vitamin D compounds1. 1. 2α-substitutionVitamins possessing 2α-substituent U that is characterized by largeconformational free energy (A value) and, therefore having this C(2)substituent in equatorial disposition and, therefore, having 1α-hydroxylin an axial orientation:

where U is selected from the group consisting of a methyl, a substitutedmethyl group described by general formula CR₁R₂R₃, an amino group orsubstituted amino group described by general formula NR₁R₂, a phosphinogroup or substituted phosphino group described by general formula PR₁R₂,an alkyl- or arylsulfinyl group, an alkyl- or arylsulfonyl group, andaryl, and where R₁, R₂ and R₃ are each independently selected from thegroup consisting of hydrogen, alkyl, hydroxyalkyl, aminoalkyl,halogenalkyl, alkoxyalkyl, aryloxyalkyl, aryl, halogen, hydroxyl,protected hydroxy, alkoxyl, aryloxyl, acyl, an amino group, an aminogroup substituted with alkyl or aryl substitutents and where R₁ and R₂,taken together, represent an oxo group, or a group —(CH₂)_(m)— where mis an integer having a value of from 2 to 5.1.2. 2α-substitution and formation of a ring with 3β-O

Vitamins that contain an anchoring bond system, i.e., possessing anadditional ring connecting C(2) with C(3)-O. The vitamins arecharacterized by trans-diequatorial orientation of substituents at C(2)and C(3) and, therefore, they have 1α-hydroxyl in an axial orientation.

where R₁ and R₂ are as described above, and wherein n is an integerhaving a value of from 1 to 4, and wherein any of the groups CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.1.3. 2-alkylidene compounds

Vitamins in which 2-methylene group is further substituted by U. Thevitamins are characterized by cis-orientation of substituents of theterminal olefinic atoms of the 1,4-dimethylenecyclohexane system of thering A, i.e. cis-orientation between C(6)–C(7) bond and C(1′)-U bond.Substituent U due to its size strongly interacts with equatorial 1α-OHand, therefore, the inverted A-ring chair conformer is favored, having1α-hydroxyl in an axial orientation:

where U is as described above with the proviso that U cannot be an —OHgroup.1.4. 2-alkylidene compounds with an additional connection with 3β-O.Vitamins that contain a flattening bond system, i.e., an exocyclic2-methylene group that is further substituted and forms a ring withC(3)-O. The vitamins are characterized by trans-orientation ofsubstituents of the terminal olefinic atoms of the1,4-dimethylenecyclohexane system of the ring A, i.e., trans-orientationbetween C(6)–C(7) bond and C(1′)–C(2′)R₁R₂ bond. Therefore, thesevitamins have C(3)-O substituent in equatorial disposition and1α-hydroxyl in an axial orientation:

where R₁ and R₂ are as described above, and wherein s is an integerhaving a value of from 1 to 3, and wherein any of the groups —CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.2. 4α-substitution and formation of a ring with 3β-OVitamins that contain an anchoring bond system, i.e., possessing anadditional ring connecting C(4) with C(3)-O. The vitamins arecharacterized by trans-diequatorial orientation of substituents at C(3)and C(4) and, therefore, they have 1α-hydroxyl in an axial orientation:

where R₁ and R₂ are as described above, and wherein n is an integerhaving a value of from 1 to 4, and wherein any of the groups —CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.3. 10β-substitutionVitamins possessing 10β-substituent U, which due to its size stronglyinteracts with C(7)-H and, therefore, the inverted A-ring chairconformer is favored, having 1α-hydroxyl in an axial orientation:

where U is as described previously.4. 1,3-diaxially bridged compounds4.1. 2β,4β-bridgedVitamins that contain a bridged bond system, i.e., possessing anadditional ring connecting C(2) with C(4). The vitamins arecharacterized by cis-1,3-diaxial orientation of additional substituentsat C(2) and C(4) and, therefore, they have 1α-hydroxyl in an axialorientation:

where R₁ and R₂ are as described above, and wherein r is an integerhaving a value of from 1 to 5, and wherein any of the groups —CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.4.2. 2β,10β-bridgedVitamins that contain a bridged bond system, i.e., possessing anadditional ring connecting C(2) with C(10). The vitamins arecharacterized by cis-1,3-diaxial orientation of substituents at C(2) andC(10) and, therefore, they have 1α-hydroxyl in an axial orientation:

where R₁ and R₂ are as described above, and wherein r is an integerhaving a value of from 1 to 5, and wherein any of the groups —CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.4.3 4β,10β-bridgedVitamins that contain a bridged bond system, i.e., possessing anadditional ring connecting C(4) with C(10). The vitamins arecharacterized by cis-1,3-diaxial orientation of additional substituentsat C(4) and C(10) and, therefore, they have 1α-hydroxyl in an axialorientation:

where R₁ and R₂ are as described above, and wherein r is an integerhaving a value of from 1 to 5, and wherein any of the groups —CR₁R₂— maybe replaced by an oxygen, sulfur or nitrogen atom.

Methods of making compounds of formulae I and 1.1–4.3 are known.Specifically, reference is made to Zhu et al, Chem. Rev. 95, 1877 (1995)and Dai et al, Synthesis 1383 (1994) which describe a method ofsynthesizing such compounds.

It should be noted in this description that the term “24-homo” refers tothe addition of one methylene group and the term “24-dihomo” refers tothe addition of two methylene groups at the carbon 24 position in theside chain. Likewise, the term “trihomo” refers to the addition of threemethylene groups. Also, the term “26,27-dimethyl” refers to the additionof a methyl group at carbon 26 and 27 positions so that for example R³and R⁴ are ethyl groups. Likewise, the term “26,27-diethyl” refers tothe addition of an ethyl group at the 26 and 27 positions so that R³ andR⁴ are propyl groups.

In the following lists of compounds, the particular substituentsattached on the A-ring should be added to the nomenclature. For example,if a methyl group is the alkyl substituent attached at the carbon 2position on the A-ring, the term “2-methyl” should precede each of thenamed compounds. If an ethyl group is the alkyl substituent attached atthe carbon 2 position on the A-ring, the term “2-ethyl” should precedeeach of the named compounds, and so on. In addition, if the methyl groupattached at the carbon 20 position is in its epi or unnaturalconfiguration, the term “20(S)” or “20-epi” should be included in eachof the following named compounds. The named compounds could also be ofthe vitamin D₂ type if desired.

Specific and preferred examples of the compounds of structure I when theside chain is unsaturated are:

19-nor-24-homo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-24-dihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-24-trihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-dimethyl-24-homo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-dimethyl-24-dihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-dimethyl-24-trihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-diethyl-24-homo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-diethyl-24-dihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-diethyl-24-trihomo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-dipropyl-24-homo-1,25-dihydroxy-22-dehydrovitamin D₃;

19-nor-26,27-dipropyl-24-dihomo-1,25-dihydroxy-22-dehydrovitamin D₃; and

19-nor-26,27-dipropyl-24-trihomo-1,25-dihydroxy-22-dehydrovitamin D₃.

Specific and preferred examples of the compounds of structure I when theside chain is saturated are:

19-nor-24-homo-1,25-dihydroxyvitamin D₃;

19-nor-24-dihomo-1,25-dihydroxyvitamin D₃;

19-nor-24-trihomo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-dimethyl-24-homo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-dimethyl-24-dihomo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-dimethyl-24-trihomo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-diethyl-24-homo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-diethyl-24-dihomo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-diehtyl-24-trihomo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-dipropyl-24-homo-1,25-dihydroxyvitamin D₃;

19-nor-26,27-dipropyl-24-dihomo-1,25-dihydroxyvitamin D₃; and

19-nor-26,27-dipropyl-24-trihomo-1,25-dihydroxyvitamin D₃.

For treatment purposes, the novel compounds of this invention defined byformula I may be formulated for pharmaceutical applications as asolution in innocuous solvents, or as an emulsion, suspension ordispersion in suitable solvents or carriers, or as pills, tablets orcapsules, together with solid carriers, according to conventionalmethods known in the art. Any such formulations may also contain otherpharmaceutically-acceptable and non-toxic excipients such asstabilizers, anti-oxidants, binders, coloring agents or emulsifying ortaste-modifying agents.

The compounds may be administered orally, topically, parenterally ortransdermally. The compounds are advantageously administered byinjection or by intravenous infusion or suitable sterile solutions, orin the form of liquid oral doses or solid doses via the alimentarycanal, or in the form of creams, ointments, patches, or similar vehiclessuitable for transdermal applications. Doses of from 0.01 μg to 100 μgper day, preferably 0.1 μg to 50 μg per day, of the compounds areappropriate for treatment purposes, such doses being adjusted accordingto the disease to be treated, its severity and the response of thesubject as is well understood in the art. Since the new compoundsexhibit specificity of action, each may be suitably administered alone,or together with graded doses of another active vitamin D compound—e.g.1α-hydroxyvitamin D₂ or D₃, or 1α,25-dihydroxyvitamin D₃—in situationswhere different degrees of bone mineral mobilization and calciumtransport stimulation is found to be advantageous.

Compositions for use in the above-mentioned cell differentiationtreatments, e.g. psoriasis and other malignancies comprise an effectiveamount of one or more vitamin D compound as defined by the above formulaI as the active ingredient, and a suitable carrier. An effective amountof such compounds for use in accordance with this invention is fromabout 0.01 μg to about 100 μg per gm of composition, and may beadministered topically, transdermally, orally or parenterally in dosagesof from about 0.1 μg/day to about 100 μg/day.

The compounds may be formulated as creams, lotions, ointments, topicalpatches, pills, capsules or tablets, or in liquid form as solutions,emulsions, dispersions, or suspensions in pharmaceutically innocuous andacceptable solvents or oils, and such preparations may contain inaddition other pharmaceutically innocuous or beneficial components, suchas stabilizers, antioxidants, emulsifiers, coloring agents, binders ortaste-modifying agents.

The compounds are advantageously administered in amounts sufficient toeffect the differentiation of promyelocytes to normal macrophages.Dosages are described above are suitable, it being understood that theamounts given are to be adjusted in accordance with the severity of thedisease, and the condition and response of the subject as is wellunderstood in the art.

The formulations of the present invention comprise an active ingredientin association with a pharmaceutically acceptable carrier therefore andoptionally other therapeutic ingredients. The carrier must be“acceptable” in the sense of being compatible with the other ingredientsof the formulations and not deleterious to the recipient thereof.

Formulations of the present invention suitable for oral administrationmay be in the form of discrete units as capsules, sachets, tablets orlozenges, each containing a predetermined amount of the activeingredient; in the form of a powder or granules; in the form of asolution or a suspension in an aqueous liquid or non-aqueous liquid; orin the form of an oil-in-water emulsion or a water-in-oil emulsion.

Formulations for rectal administration may be in the form of asuppository incorporating the active ingredient and a carrier such ascocoa butter, or in the form of an enema.

Formulations suitable for parenteral administration convenientlycomprise a sterile oily or aqueous preparation of the active ingredientwhich is preferably isotonic with the blood of the recipient.

Formulations suitable for topical administration include liquid orsemi-liquid preparations such as liniments, lotions, applicants,oil-in-water or water-in-oil emulsions such as creams, ointments orpastes; or solutions or suspensions such as drops; or as sprays.

For asthma treatment, inhalation of powder, self-propelling or sprayformulations, dispensed with a spray can, a nebulizer or an atomizer canbe used. The formulations, when dispensed, preferably have a particlesize in the range of 10 to 100μ.

The formulations may conveniently be presented in dosage unit form andmay be prepared by any of the methods well known in the art of pharmacy.The term “dosage unit” is meant a unitary, i.e. a single dose which iscapable of being administered to a patient as a physically andchemically stable unit dose comprising either the active ingredient assuch or a mixture of it with solid or liquid pharmaceutical diluentes orcarriers.

In its broadest application, the present invention relates to any analogof vitamin D which have the vitamin D nucleus. By “vitamin D nucleus”,it is meant a central part consisting of a substituted chain of fivecarbon atoms which correspond to positions 8, 14, 13, 17 and 20 ofvitamin D₃ and at the ends of which are connected at position 20 astructural moiety representing any of the typical side chains known forvitamin D type compounds (such as R as previously defined herein), andat position 8 the 5,7-diene moiety connected to the A-ring of an active1α-hydroxy vitamin D analog (as illustrated by formula I herein). Thus,various known modifications to the six-membered C-ring and thefive-membered D-ring typically present in vitamin D₃ such as the lack ofone or the other or both, are also embraced by the present invention.

Accordingly, compounds of the following formulae Ia, are along withthose of formula I, also encompassed by the present invention:

In the above formula Ia, the definitions of Y₁, Y₂, Y₃, Y₄, Y₅, Y₆, Y₇,Y₈ and Z are as previously set forth herein. With respect to X₁, X₂, X₃,X₄, X₅, X₆, X₇, X₈ and X₉, these substituents may be the same ordifferent and are selected from hydrogen or lower alkyl, i.e. a C₁₋₅alkyl such as methyl, ethyl or n-propyl. In addition, pairedsubstituents X₁ and X₄ or X₅, X₂ or X₃ and X₆ or X₇, X₄ or X₅ and X₈ orX₉, when taken together with the three adjacent carbon atoms of thecentral part of the compound, which correspond to positions 8, 14, 13 or14, 13, 17 or 13, 17, 20 respectively, can be the same or different andform a saturated or unsaturated, substituted or unsubstituted,carbocyclic 3, 4, 5, 6 or 7 membered ring.

Preferred compounds of the present invention may be represented by oneof the following formulae:

In the above formulae Ib, Ic, Id, Ie, If, Ig and Ih, the definitions ofY₁, Y₂, Y₃, Y₄, Y₅, Y₆, Y₇. Y₈, R, Z, X₁, X₂, X₃, X₄, X₅, X₆, X₇ and X₈are as previously set forth herein. The substituent The substituent Qrepresents a saturated or unsaturated, substituted or unsubstituted,hydrocarbon chain comprised of 0, 1, 2, 3 or 4 carbon atoms, but ispreferably the group —(CH₂)_(k)— where k is an integer equal to 2 or 3.

Methods for making compounds of formulae Ia–Ih are known. Specifically,reference is made to International Application Number PCT/EP94/02294filed 7 Jul. 1994 and published 19 Jan. 1995 under InternationalPublication Number WO95/01960.

1. A compound having the formula:

where R₁ and R₂ are each independently selected from the groupconsisting of hydrogen, alkyl, hydroxyalkyl, aminoalkyl, halogenalkyl,alkoxyalkyl, aryloxyalkyl, aryl, halogen, hydroxyl, protected hydroxy,alkoxyl, aryloxyl, acyl, an amino group, an amino group substituted withalkyl or aryl substituents and where R₁ and R₂, taken together,represent an oxo group, or a group —(CH₂)_(m)— where m is an integerhaving a value of from 2 to 5; and wherein r is an integer having avalue of from 1 to 5, and wherein any of the groups CR₁R₂— may bereplaced by an oxygen, sulfur or nitrogen atom; and R is represented bythe structure below

where the stereochemical center at carbon 20 may have the R or Sconfiguration, and where Z is selected from Y, —OY, —CH₂OY, —C≡CY and—CH═CHY, where the double bond may have the cis or trans geometry, andwhere Y is selected from hydrogen, methyl, —COR₁₀ and a radical of thestructure:

where x and y, independently, represent the integers from 0 to 5, whereR₆ is selected from hydrogen, deuterium, hydroxy, protected hydroxy,fluoro, trifluoromethyl, and C₁₋₅-alkyl, which may be straight chain orbranched and, optionally, bear a hydroxy or protected-hydroxysubstituent, and where each of R₇, R₈, and R₉, independently, isselected from deuterium, deuteroalkyl, hydrogen, fluoro, trifluoromethyland C₁₋₅ alkyl, which may be straight-chain or branched, and optionally,bear a hydroxy or protected-hydroxy substituent, and where R₆ and R₇,taken together, represent an oxo group, or an alkylidene group, ═CR₇R₈,or the group —(CH₂)_(p)—, where p is an integer from 2 to 5, and whereR₈ and R₉, taken together, represent an oxo group, or the group—(CH₂)_(q), where q is an integer from 2 to 5, and where R₁₀ representshydrogen, hydroxy, protected hydroxy, or C₁₋₅ alkyl and wherein any ofthe CH-groups at positions 20, 22, or 23 in the side chain may bereplaced by a nitrogen atom, or where any of the groups —CH(CH₃)—,—(CH₂)_(x)—, —(CR₆R₇)— or —(CH₂)_(y)— at positions 20, 22, and 23,respectively, may be replaced by an oxygen or sulfur atom.
 2. Apharmaceutical composition containing an effective amount of at leastone compound as claimed in claim 1 together with a pharmaceuticallyacceptable excipient.
 3. The pharmaceutical composition of claim 2 indosage unit form.
 4. The pharmaceutical composition of claim 3containing about 0.01 μg to about 100 μg of said at least one compound.5. The pharmaceutical composition of claim 2 in topical form.
 6. Thepharmaceutical composition of claim 2 in oral form.
 7. A method oftreating metabolic bone disease where it is desired to maintain orincrease bone mass comprising administering to a patient with saiddisease an effective amount of a compound as claimed in claim
 1. 8. Themethod of claim 7 where the disease is senile osteoporosis.
 9. Themethod of claim 7 where the disease is postmenopausal osteoporosis. 10.The method of claim 7 where the disease is steroid-induced osteoporosis.11. The method of claim 7 where the disease is low bone turnoverosteoporosis.
 12. The method of claim 7 where the disease isosteomalacia.
 13. The method of claim 7 where the disease is renalosteodystrophy.
 14. The method of claim 7 where the disease is rickets.15. The method of claim 7 where the disease is vitamin D resistantrickets.
 16. The method of claim 7 wherein the compound is administeredorally.
 17. The method of claim 7 wherein the compound is administeredparenterally.
 18. The method of claim 7 wherein the compound isadministered transdermally.
 19. The method of claim 7 wherein thecompound is administered in a dosage of from 0.1 μg to 50 μg per day.